Automatic speed change device for vehicles



Jan. 13, 1970 YOICHI MORI ET AL AUTOMATIC SPEED CHANGE DEVICE FORVEHICLES 8 Sheets-Sheet 1 Filed July 18, 1967 Jan. 13, 1970 YOICHIMQRI'E AL AUTOMATIC SPEED CHANGE DEVICE FOR VEHICLES Filed July 18, 19678 Sheets-Sheet 2 Jan. '13, I970 YOlCHl MORI ET AUTOMATIC SPEED CHANGEDEVICE FOR VEHICLES Filed July 18, 1967 8 Sheets-$heet 3 YOlCHl MORI ETAL AUTOMATIC SPEED CHANGE DEVICE FOR VEHICLES Jan. 13, 1970 8Sheets-Sheet 4 Filed July 18, 1967 Jan. 13, 1970 YOICHI MORI ET AL3,489,037

AUTOMATIC SPEED CHANGE DEVICE FOR VEHICLES Filed July 18, 1967 8Sheets-Sheet 5 YOlCHl MORI ET AL AUTOMATIC SPEED CHANGE DEVICE FORVEHICLES Jan. 13, 1970 8 Sheets-Sheet 6- Filed July 18, 1967 Jan.13,1970 YOICHI MORI ET AL AUTOMATIC SPEED CHANGE DEVICE FOR VEHICLES 8Sheets-Sheet 7 Filed July 18, 1967 Jan. 13, 1970 YOICHI m ET ALAUTOMATIC SPEED CHANGE DEVICE FOR VEHICLES 8 Sheets-Sheet 8 Filed July18, 1967 United States Patent 3,489,037 AUTOMATIC SPEED CHANGE DEVICEFOR VEHICLES Yoichi Mori, Nagayuki Marumo, Noburu Fukazawa, and KoichiOhie, Yokohama, Japan, assignors to Nissan Jidosha Kahushiki Kaisha,Yokohama, Japan Filed July 18, 1967, Ser. No. 654,231 Claims priority,application Japan, July 30, 1966, ll/49,650, 41/49,649; Sept. 27, 1966,41/631,386 Int. Cl. F16h 37/08 US. Cl. 74-695 Claims ABSTRACT OF THEDISCLOSURE A speed change device for vehicles comprising a torqueconverter connected to an engine crankshaft, a clutch means, a planetarygear assembly means selectively connectable to said torque converterthrough said clutch means, a brake and one-way brake means selectivelyengageable with said planetary gear assembly means, an output gearlocated at a point corresponding to the longitudinal middle point ofsaid crankshaft, wherein axes of said clutch means, said planetary gearassembly means, said brake and one-way brake means, and said output gearare in alignment with a common axis which is parallel with the axis ofsaid crankshaft.

This invention relates to an automatic speed change device for vehicles,more particularly to a speed change device for vehicles comprising atorque converter connected to an engine crankshaft, a clutch means, aplanetary gear assembly means selectively connectable to said torqueconverter through said clutch means, a brake and one-way brake meansselectively engageable with said planetary gear assembly means, and anoutput gear located at a point corresponding substantially to thelongitudinal middle point of said crankshaft, wherein axes of said'clutch means, said planetary gear assembly means, said brake and one-waybrake means, and said output gear are in alignment with a common axiswhich is parallel with the axis of said crankshaft.

At the present, the most commonly used layout of power transmissionmechanism in a vehicle is the 50+ called front-engine rear-drive type,in which the engine for driving the vehicle is placed in the proximityof the front axle of the vehicle and the speed change device ispositioned directly behind the engine, so that the engine power istransmitted to the rear wheels through a propeller shaft, a differentialgear means, and rear axles. In the front-engine rear-drive type layout,the propeller shaft is indispensable.

In order to eliminate the need of such propeller shaft, it has beenproposed and practiced to some extent to use the so-called front-enginefront-drive type or rear-engine rear-drive type layout. However, whenthe propeller shaft is eliminated by using the latter type layout, theoverall set up of the vehicle driving mechanism becomes complicated,because a number of driving and power transmitting devices, such as theengine, the speed change device, the differential gear means, driveaxles, etc., have to be arranged effectively in a limited space. Inorder to achieve the smooth operation of the vehicle, it is necessary toplace the differential gear means at about the middle point between thedrive wheels on both sides of the vehicle or about the middle point ofthe drive axle leading to the drive wheels. With conventional speedchange devices for a front-engine front-drive type or rear-enginerear-drive type vehicle, it has been difficult to place the differentialgear means at the middle point of the drive axle to ensure smoothoperation of the vehicle.

"ice

The principal object of the present invention is to obviate suchdifficulty of the last mentioned conventional speed change devices byproviding a novel speed change device which is adapted to produce outputpower at a point corresponding to the longitudinal middle point of thedriving engine.

With the speed change device according to the present invention, it ispossible to mount the driving engine laterally to the travellingdirection of the vehicle or placing the axis of the crankshaft of theengine at right angles to the travelling direction of the vehicle.

The most salient feature of the speed change device of the presentinvention is in the fact that the device can be so fitted in the powertransmission system of the vehicle that the differential gear means canbe readily placed at the middle point of the drive axle.

According to the present invention there is provided an automatic speedchange device which comprises a torque converter connected to one end ofthe crankshaft of an engine, a first and a second clutch driven by saidtorque converter, a planetary gear assembly means selec tivelyengageable with said first and second clutches, said planetary gearassembly having elementary gears including at least a sun gear, aplurality of planet gears, an internal gear, and a carrier supportingsaid planet gears, brake and one-way brake means to automatically stopsaid elementary gears of the planetary gear assembly means in aselective manner, and an output gear to be driven by said planetary gearassembly means, axes of rotation of said clutches, said planetary gearassembly means, said brake and one-way brake means, and said output gearbeing in alignment with a common axis which is parallel with the axis ofsaid crankshaft of the engine, said output gear being located at aposition on said common axis which corresponds substantially to thelongitudinal middle point of the crankshaft.

The advantages of the speed change device according to the presentinvention will be summarized as follows:

(1) The output power from the speed change device can be obtained atabout the middle point of the axis of an engine crankshaft, which drivesthe speed change device. Accordingly, if the engine and the speed changedevice are mounted laterally on a vehicle, it is ensured that adifferential gear means can be positioned at about the middle point ofboth side drive wheels of a vehicle or at about the middle point of thedrive axle leading t the drive wheels.

(2) The construction of the speed change device itself is very simple,because a comparatively small number of gears are involved therein. Withthe speed change device of the invention, the propeller shaft of theconventional power transmission system of a vehicle can be eliminated. t

(3) With the use of one-way brake means, the shift from one operativestage to another operative stage of the speed change device can becarried out smoothly.

(4) Throughout the forward stages of operation, the first clutch is keptengaged, and hence, even though minor switch-over of the brake means andthe clutch means takes place, the major connection from the power inputmembers to the planetary gear assembly is kept unchanged. Thus, thesmooth operation of the vehicle can be ensured.

(5) The power output member is not switched over throughout the entirestages of operation, so that the structure of the overall transmissionsystem is very simple.

(6) During idling, the speed change device can be held at the so-calledclean neutral position, or the power transmission from the engine to theplanetary gear assembly means is completely interrupted at the clutchmeans.

Accordingly, mechanical noise during the idling of the speed changedevice can be minimized.

(7) Identical mechanical parts can be used at different portions of thespeed change device, when two units of simple planetary gear assembliesare used therein. Thereby, the manufacturing cost of the speed changedevice can be reduced.

(8) The particular mechanical structure of the device allows thedesigner to select speed change ratios at will for each operative stage,so that the optimum speed change ratios can be easily providedthroughout the entire operative stages. Thus, the efficiency of thespeed change device can be improved and the mechanical loading to thecomponent gears can be reduced.

For a better understanding of the invention, reference is made onaccompanying drawings, in which:

FIG. 1 is a simplified skeleton diagram of the first embodiment of theautomatic speed change device according to the present invention;

FIGS. 2 to 4 are views similar to FIG. 1, illustrating differentmodifications of the first embodiment;

FIG. 5 is a diagrammatic illustration of the manner in which variouselementary gears in the planetary gear assembly usable in the firstembodiment of the speed change device are related with each other;

FIG. 6 is a simplified schematic skeleton diagram of the secondembodiment of the automatic speed change device according to the presentinvention;

FIGS. 7 to 9 are skeleton diagrams, showing different modifications ofthe second embodiment;

FIG. is a diagrammatic illustration similar to FIG. 5, showing themanner in which various elementary gears of a planetary gear assemblyusable in the second embodiment as shown in FIGS. 6 to 9 are relatedwith each other;

FIGS. 11 to 13 are skeleton diagrams illustrating different forms of thethird embodiment of the invention, in which two units of simpleplanetary gear assemblies are utilized;

FIG. 14 is a view similar to FIG. 13, showing a fourth embodiment of theinvention; and

FIG. is a schematic sectional view of an arrangement of various parts ofthe fourth embodiment of the speed change device according to thepresent invention.

The same reference numerals and the same symbols represent thecorresponding parts of the speed change device throughout the drawings.

The first embodiment of the automatic speed change device according tothe present invention will now be described referring to FIG. 1. In thefigure, an engine crankshaft 1 is shown as that of a piston engine, butit can be a driving shaft of a non-piston engine, such as a rotaryengine. A torque converter V directly connected to one end of the enginecrankshaft 1 comprises a pump 2 secured to the crankshaft 1, turbine 3,a stator 4, and a one-way brake 5. The one-way brake 5 is mounted on asleeve 6, which is integral with the casing of the speed change device.A series of transmission gears 8 to 10 are provided between the torqueconverter V and an input shaft 11, in which the gear 8 is driven by theturbine 3 through a hollow shaft 7, while the gear 9 acts to transferthe rotation of the gear 8 to the gear 10 secured to the input shaft 11.The one-way brake 5 is adapted to allow the rotation of the stator 4only in the normal direction, but not in the opposite direction. What ismeant by the normal direction is that direction in which the crankshaft1 and the pump 2 rotate.

The speed change device according to the present invention includesfrictional and gearing elements depicted by reference numerals 11 to 34.A clutch body 12, which is common to both a first and a second clutch,is integral with the input shaft 11, and first clutch plate 14 and asecond clutch plate 13 are selectively engageable with the common clutchbody 12. The first clutch plate 14 is connected to a transmission shaft16, while the second clutch plate 13 is secured to another hollow shaft15 adapted to rotate around the transmission shaft 16 in a slidingmanner. Connected to the shafts 15 and 16 is a Ravigneaux type planetarygear assembly having a first sun gear 17 connected to the shaft 16, asecond sun gear 18 connected to the hollow shaft 15, first planet gears19, second planet gears 20, an internal gear 21 and a carrier 22supporting the first and second planet gears 19 and 20 in a rotatable'nanner. What is meant by the Ravigneaux type planetary gear assembly,for instance, is an'assembly' as disclosed in the US. Patent No.2,239,973, granted to P01 Ravigneaux on Apr. 29, 1941. FIG. 5 shows anexample of such planetary gear assembly usable in'the speed changedevice according to the present invention, in which the first sun gear17 is meshed with first planet gears 19, the second sun gear 18 ismeshed with second planet gears 20, the second planet gears 20 arefurther meshed with both the first planet gears 19 and the internal gear21, and the carrier 22 carries the first and second planet gears 19 and20 in a rotatable manner around the axis of the assembly and around theaxes of the planet gears.

There is provided another one-way brake 23, which allows rotation of thecarrier 22 only in the aforesaid normal direction. When the carrier 22tends to rotate in a non-normal direction, the one-way brake 23 isactuated to stop the carrier 22 against such tendency. A brake 24 actsto stop the rotation of the hollow shaft 15 and accordingly rotation ofthe second sun gear 18, and another brake 25 acts to stop the carrier22, when they are actuated. An output pinion 27 is connected to theinternal gear 21 through another hollow shaft 26, which is adapted torotate around the hollow shaft 15.

A reducing gear wheel 28 is driven by the output pinion 27 so as toactuate a differential gear means consistingof gears 29 to 32. Driveaxles 33 and 34 are rotated by the differential gear means to turn thedrive wheels (not shown) located at both sides of a vehicle. Generallyspeaking, in the case of front-drive type layout, the drive axles 33 and34 are connected to drive wheels through universal joints respectively,while in the case of reardrive type layout, the drive axles 33 and 34are directly connected to the drive wheels at both sides of the vehicle.The differential gear means comprises a pair of bevel pinions 29 and 30carried by pins 28' and 28" mounted on the reducing gear wheel 28, and apair of side gears 31 and 32 coupled with both side drive axles 33 and34 respectively. The side gears 31 and 32 are driven by the bevel gears29 and 30, and under differential operative conditions, one side gear,e.g. the gear 31, is rotated at a different speed from that of the otherside gear, e.g. the gear 32.

It is important to note here that axes of rotation of the clutches 12,13, and 12, 14, the planetary gear assembly, the brakes 24 and 25, theone-way brake 23, and the out"- put pinion 27, should be aligned with acommonaxis, which is the shaft line of the shafts 11, 15, and 16.Moreover, this common axis is parallel with both the axis of thecrankshaft 1 and axles 33 and 34.

With the speed change device of the aforesaid construction, when theengine crankshaft 1 is rotated by starting the engine, the engine poweris transferred to the pump 2 of the torque converter V, and further tothe turbine 3 by means of the fluid flowing through the torque converterV. The power on the turbine 3 is transmitted to the clutch body 12common to both first and second clutches by means of the hollow shaft 7,the series of transmission gears 8 to 10, and the input shaft 11 to theclutch means.

By actuating automatically each clutch and each brake Prior to enteringinto the detailed explanation of the operative conditions of eachclutch, each brake, power transmission routes, and speed change ratiosfor each operative stage of the speed change device, description will bemade on the relations between revolving speeds of various rotary membersof the device, which are necessary for determination of the speed changeratios for each operative stage. Let it be assumed that the revolvingspeeds of the first sun gear 17, the second sun gear 18, the internalgear 21, and the carrier 22 are represented by S S R, and C,respectively. Then, there are following relations among such revolvingspeeds.

(pitch circle radius of the internal gear 21) (pitch circle radius ofthe first sun gear 17) Z (pitch circle radius of the second sun gear 18)s (pitch circle radius of the first sun gear 17) As will be described indetail hereinafter, in the case of forward operation of the speed changedevice, the power on the turbine 3 is delivered to the first sun gear 17because the first clutch 12, 14 is engaged, While in the case of therearward operation, the power on the turbine 3 is transferred to thesecond sun gear 18 as the second clutch 12, 13 is engaged. Accordingly,the speed change ratio for the forward operation is defined by thequotient of S /R, and that for the rearward operation is defined by thequotient of S /R.

If it is further assumed that the pitch circle radii of the transmissiongears 8 and are the same, then the revolving speed S or S becomesidentical with that of the turbine 3. The output pinion 27 and theinternal gear 21 are rotated always at the same speed, because they arebonded together. Hence, the speed change ratios given by S /R and S /Ralso represent the speed change ratios between the turbine 3 and theoutput pinion 27 under the aforesaid assumptions.

The speed change ratios for each operative stage can be determined bysubstituting zero to that revolving speed in the Formulae a and ,8 whichrepresents a rotary member that is held stationary in the particularstage of operation.

The operation of the speed change device in each operative stage willnow be described. In the following description, it is assumed, for thesake of numerical examples, that I =2.4O and I 1.14.

NEUTRAL STAGE Both the first and second clutches are released. In thiscase, the cpmmon clutch body idles, and the power on the turbine is nottransmitted to any rotary member further than the clutch body 12.

FORWARD FIRST STAGE The first clutch 12, 14 is engaged. In this case,the power on the turbine 3 is delievered to the firstsun gear 17, andthe carrier 22 tends to be rotated in the nonnormal direction by thefrictional force between the drive wheels .(not shown) and the roadsurface (not shown),

but the one-way brake 23 acts to hold the carrier 22 stationary againstsuch tendency. By substituting the relation of C=0 to the Formula u, thespeed change ratio m for the forward first stage can be determined asfollows.

In other words, the output pinion 27 rotates at a speed lower than thatof the first sun gear 17. The revolving speed of the first sun gear 17is the same as that of the turbine 3 in this embodiment. The power onthe output pinion 27 is delievered to the reducing gear wheel 28 at areduced speed, and then'further to the driving wheels (not shown) atboth sides of the vehicle through the differential gear means connectedto the drive axles 33 and 34.

FORWARD SECORND STAGE The first clutch 12, 14 is engaged and at the sametime the brake 24 is actuated. Under these conditions, the power on theturbine 3 is transmitted to the first sun gear 17 as in the case of theforward first stage, while the second sun gear 18 is held stationary bymeans of the brake 24. By substituting the relation of S 0 to theFormulae a and ,8, the speed change ratio In for this operative stagecan be determined as follows.

bras-b m S IR ZR+ZS 1.45

Since the transmission route of power from the output pinion 27 to thedrive wheels (not shown) is identical to that in the case of the forwardfirst stage operation, it will not be repeated in the description of theforward second and succeeding operative stages.

FORWARD THIRD STAGE m=S /R=S /R=1 In other Words, the entire planetarygear assembly and the output pinion 27 rotate as an integral body at acommon revolving speed.

REARWARD STAGE The second clutch 12, 13 is engaged, while the brake 25is actuated. Under these conditions, the power on the turbine 3 isdelivered to the second sun gear 18 through thus engaged clutch 12, 13and the hollow shaft 15. By substituting the relation of C,=0. to theFormulae a and 13, the speed change ratio for this operative stage canbe determined as follows.

In other words, the output pinion 27 rotates in a reverse direction at areduced speed.

The operative conditions of each clutch and brake in.

the aforesaid operative stages of the speed change device are shown inTable I.

TABLE I Forward Forward Forward Rearward Operative stage 1st stage 2dstage 3d stage stage First clutch (12, 14) Epgaged Etlgaged EngagedDisengaged. Second clutch (12, 13) D1sengaged- Dlseng ged .do Engaged.Brake (24) Not actuated..- Actuated Not actuated. Not actuated. Brake(25) .-v (Actuated) Not actuated .do Actuated. One-way brake (2 3)... Au ed 0 -do Not actuated. Speed Change ratio (m Formula ZR n(s+l)lln+ls.- 1 lR/ls. Example:

Note: In Table I, the reason for parenthesizing the actuated conditionof the brake 25 in the forward first stage is as follows. When enginebraking is applied, for instance for the purpose of controlling thetravelling speed of a vehicle while descending along a slope, there isproduced such a torque on the output pinion which tends to acceleraterotation of the carrier 22 in the normal direction. Since the one-waybrake 23 is not effective in hindering the rotation of the carrier inthe normal direction, in order to make the engine brake effective, it ispreferable to actuate the brake 25 to withhold the carrier 22 securely.

Thus, the desired engine braking can be applied while maintaining thefirst speed change ratio.

FIG. 2 illustrates a modification of the speed change device as shown inFIG. 1, in which a first clutch 12, 14 and a second clutch 12, 13 areseparated and located at opposite sides of the planetary gear assembly.The operative principles of the speed change device of FIG. 2 areidentical with those of FIG. 1, and hence, the conditions of Table I arealso applicable to this modification. The advantage of this modificationis in the fact that the torque converter V can be connected to the righthand end of the crankshaft 1, as viewed in FIG. 2, so that the drivingtorque can be delivered to the planetary gear assembly from the righthand end of the input shaft 11, even though the example of FIG. 2 has atorque converter connected to the extreme left end of the crankshaft 1.In this modification, a transmission shaft 16, which cor responds to theshaft 16 of the preceding embodiment, should be hollow.

FIG. 3 shows a further modification of the speed change device as shownin FIG. 2, in which the combination of a one-way brake 23, brakes 24 and25 is arranged between a second clutch 12, 13 and a planetary gearassembly, while an output pinion 27 is disposed between the planetarygear assembly and a first clutch 12, 14. The conditions of Table I arealso applicable to this embodiment. The advantage of this modificationis also in the fact that the driving torque from the engine crankshaft 1can be transmitted to the planetary gear assembly through either lefthand end or the right hand end of the input shaft 11.

FIG. 4 shows a modification of the speed change device as depicted inFIG. 1, in which the relative positions between first and the second sungears are interchanged and a brake 24 associated with the second sungear 18 is positioned at the extreme right end of the speed changedevice. In this modification, a shaft 15', which corresponds to thehollow shaft 15 of FIG. 1, can be made solid. The operative conditionsof Table I are also applicable to this modification. The advantage ofthe modification as illustrated in FIG.' 4 is in the fact thatfrictional elements including brakes 24 and 25 and a one-way brake 23are concentrated at the right hand end of the input shaft 11.

As described in the foregoing referring to FIGS. 1 to 5, in the firstembodiment of the speed change device according to the presentinvention, the output power is transmitted to the drive axles 33, 34disposed in parallel with the common axis, which is common to theplanetary gear assembly, clutches and brakes. Furthermore, the aforesaidcommon axis and the drive axles are both arranged in parallel with theaxis of the crankshaft 1. In other words, the power system to drivewheels in this vehicle comprises three parallel axes, namely those ofthe crankshaft, the gears of the speed change device, and

the drive axles. Such arrangement of power system is particularlyadvantageous for the aforesaid lateral layout of the engine in afront-engine front-drive type vehicle or a rear-engine rear-drive typevehicle. In this first embodiment of the invention, a pair of clutches12, 13 and 12, 14 are inserted respectively between the input shaft 11and the first sun gear 17 and between the input shaft' 11 and the secondsun gear 18, while the output pinion 27 is dispsed...either between thepair of clutches and the planetary gear assembly or between one of thepair of clutches and the planetary gear assembly. Here, the positionofthe output pinion 27 corresponds to the longitudinal middle point ofthe crankshaft 1. With the output pinion 27 thus disposed at anintermediate position among mechanical elements of the speed changedevice according to the present invention, a differential gear meanscomprising gears 28, 29, 30, 31, and 32 can be placed at about themiddle of the wheels (not shown) on both sides of the vehicle.Accordingly, both side drive axles 33 and 34 can be made in about thesame length.

With the modifications shown in FIGS. 2 to 4, this embodiment of thespeed change device can be mounted on various kinds of vehicles whichhave a variety of requirements on dimensions and layout of thestructural components of the speed change device due to particular bodyand engine construction of the vehicles. Thus, most suitable layout ofthe power transmission can be achieved in vehicles of variousconstruction,

In the preceding examples, the planetary gear assembly had two sun gearsand an internal gear. The present invention, however, is not limited tosuch planetary gear assembly only.

FIG. 6 shows a second type embodiment of the present invention, which isessentially of the same structure as the first embodiment as describedhereinbefore referring to FIGS. 1 to 5, except that the structure of theplanetary gear assembly and the mechanical connections related theretoare modified. The input portion of the second embodiment, whichtransmits power from an engine crankshaft 1 to an input shaft 11connected to clutches, is identical with that of the first embodiment,and hence, the details of the structure and the operation of the inputportion will not be repeated here.

A modified Ravigneaux type planetary gear assembly, as will be describedhereinafter, is used in the second embodiment. As shown in FIG. 6, theplanetary gear assembly comprises a first internal gear 41, a secondinternal gear 42, first planet gears 19, second planet gears 20, a sungear 43, and a carrier 22 supporting the planet gears 19 and 20 in arotatable manner. Let it be assumed that in the modified Ravigneaux typeplanetary gear assembly, the elementary gears are meshed with each otheras shown in FIG. 10; namely, the first internal gear 41 is meshed withthe first planet gears 19, and the second internal gear 42 is meshedwith the second planet gears 20, while the first planet gears 19 aremeshed with both the sun gear 43 and the second planet gears 20, whereinthe first and the second planet gears are rotatably supported by thecarrier 22 at certain geometrical relations between each other.

The sun gear 43 of the modified Ravigneaux type planetary gear assemblyis connected to the input shaft 11 through a hollow shaft 15 connectedto a second clutch 12, 13, while the first internal gear 41 is bonded toa transmission shaft 16 connected to a first clutch 12,

14. The construction and operation of the first and the second clutchesand the shafts between the clutches and the planetary gear assembly arethe same as the corresponding clutches and shafts of the firstembodiment,

hence, no detailed explanation thereof will be repeated here. A one-waybrake 23 is mounted on the casing 35 of the device so as to support thesecond internal gear 42 in such a manner that the second internal gear42 can be rotated in the normal direction but not in the oppositedirection.

The brake 24 acts to hold the hollow shaft 15 and accordingly the sungear 43 when it is actuated, while the brake25 acts to hold the secondinternal gear 42 stationary when it is actuated. An output pinion 27 isconnected to the carrier 22 through a hollow shaft 26 so as to berotated as an integral body therewith. The hollow shaft 26 is adapted torevolve around the hollow shaft 15.

The construction and the operation of the power transmission routesubsequent to the reducing gear wheel 28, which is meshed with theoutput pinion 27, are the same 9 as those of the first embodiment asdescribed hereinbefore referring to FIGS. 1 to 4.

With the speed change device of the aforesaid con struction, when theengine crankshaft 1 is driven by starting the engine, the power istransmitted to the turbine 3 of the torque converter V through the pump2 and the fluid flowing within torque converter V, and the power on theturbine 3 is further delivered to the common clutch body 12 of the firstand second clutches through the hollow shaft 7 connected to the seriesof transmission gears 8 to 10 and the input shaft 11 of the speedchanging means. By controlling automatically the operative condi tionsof the clutches and the brakes with a suitable hydraulic means (notshown), the revolving speed of both the carrier 22 of the planetary gearassembly and the output pinion 27 can be changed in three stages inforward direction and in one stage in the rearward direction. Thuschanged revolving speed of the output pinion 27 is further reduced bythe reducing gear wheel 28 and the power is delivered to the drive axles33 and 34 at both sides of the vehicle through said gear wheel and thedifferential gear means.

Prior to entering the detailed description of the operation of eachclutch and brake, the power transmission routes, and speed change ratiosfor each operative stage of the speed change device, the relationsbetween revolving speeds of various gear members of the device will nowbe described. Assuming that the revolving speeds of the sun gear 43, thefirst internal gear 41, the second internal gear 42 and the carrier 22are represented by S, R1, R and C respectively, then there are followingrelations among such revolving speeds.

Here,

I (pitch circle radius of the first internal gear 41) If (pitch circleradius of the sun gear 43) Z (pitch circle radius of the second internalgear 42) 2 (pitch circle radius of the sun gear 43) As will be describedhereinafter, in the case of forward operation, the forward clutch 12, 14is engaged, and the power on the turbine 3 is transmitted to the firstinternal gear 41 through thetransmission shaft 16, while in the case ofthe rearward operation, the rearward clutch 12, 13 is engaged so thatthe power is delivered to the sun gear 43 through the hollow shaft 15.Accordingly, the speed change ratio can be designated by R /C in thecase of the forward operation, and S/C in the caseof the rearwardoperation. If it is assumed here that the pitch circle radii of thetransmission gears 8 and are the same, then the revolving speed R or Sbecomes identical with the revolving speed of the turbine 3. Since therevolving speed of the output pinion 27 is identical with that of thecarrier 22, each of the aforesaid speed change ratios R C and S/ Cbecomes the speed change ratio between the turbine 3 and the outputpinion 27. The speed change ratios for each operative stage can bedetermined by substituting zero to the revolving speed in the Formulae(u) and (/3) which represents a rotary member that is held stationary inthe particular stage of operation. 1

Each operative stage of the speed change device will now be described indetail. In the numerical examples in the following description it isassumed that :24 and 1 :32.

NEUTRAL STAGE Both the first and the second clutches are disengaged.Under these conditions, the clutch body 12 idles, and the power is nottransmitted any further.

10 FORWARD FIRST STAGE The first clutch 12, 14 is engaged. In this case,the power on the turbine 3 is transmitted to the first internal gear 41.The second internal gear 42 tends to be turned in non-normal directionby the friction between the drive wheel and the road surface, but theone-way brake 23 acts to held the second internal gear 42 stationaryagainst such tendency due to the frictional force. By substituting therelation of R =0 to the Formulae (04) and (,B), the speed change ratio mfor this operative stage can be determined as follows.

In other words, the output pinion 27 rotates at a speed lower than thatof the first internal gear 41 or that of the turbine 3. The power on theoutput pinion 27 is deliver to both side axles 33 and 34 through thereducing gear wheel 28 so as to actuate the drive wheels (not shown) onboth sides of the vehicle.

FORWARD SECOND STAGE The first clutch 12, 14 is engaged, and at the sametime the brake 24 is actuated. Under such conditions, the power on theturbine 3 is transmitted to the first internal gear 41 as in the case offorward first stage, and the sun gear 43 is held stationary by the brake24. By substituting the relation of S=0 to the Formulae (04), the speedchange ratio In for the forward second stage can be determined asfollows.

In this stage, the output pinion 27 rotates also at a speed lower thanthat of the first internal gear 41. Since the power transmission routefrom the output pinion 27 to the drive wheels (not shown) is identicalwith that in the case of the forward first stage operation, it will notbe repeated in the description of the forward second and the succeedingoperative stages.

FORWARD THIRD STAGE Both the first and the second clutches 12, 14 and12, 13 are engaged simultaneously, but no brake is actuated. Under theseconditions, the power on the turbine 3 is delivered simultaneously toboth the sun gear 43 and the first internal gear 41. By substituting therelation of S=R to the Formula (0a), the speed change ratio m for thisforward third stage is given by I In other words, the entire planetarygear assembly and the output pinion 27 revolve together as an integralbody.

REARWARD STAGE The second clutch 12, 13 is engaged, and the brake 25 isactuated. Under these condtions, the power on the turbine 3 is deliveredto the sun gear 43 through the rearward clutch 12, 13 and the hollowshaft 15, while the second internal gear 18 is held stationary by thebrake 25. Therefore, by substituting the relation of R =0 to the Formula(6), the speed change ratio m for this rearward stage can be given asfollows.

In other words, the output pinion 27 is rotated in the reverse directionat a reduced speed.

The operative conditions and the speed change ratio in each operativestage of the speed change device as shown in FIG. 6 are summarized inTable II.

TABLE II Forward Forward Forward Rearward Operative stage 1st stage 2dstage 3d stage stage First clutch (12, 14) Engaged Engaged EngagedDisengaged. Second clutch (12, 13) Disengaged Disengaged EngagedEngaged- Brake (24) Not actuatednn Actuated Not aotuated. Not actuated.Brake (25) (Actuated) Notactuated -do Actuated. One-way brake (23)"Actuated d do N'ot actuated. Speed change ratio (m Formula lrl-Zz/l; l-l-l/l 1 (l2l). EXainplZe;

Note: In Table II, the reason for parenthesizing the actuated conditionof the brake 25 in the forward first stage is the same as what wasdescribed in detail in the note to Table I, provided that the carrier 22in the note to Table I should be substituted by the second internal gear42 in the case of the second embodiment as shown in FIG. 6.

A modification of the second embod'ment is shown in FIG. 7, in which thefirst clutch 12', 14 and a second clutch 12, 13 are not made in anintegral mechanism but divided into two separate mechanisms and disposedat opposite ends of the planetary gear assembly, respectively. Theoperative principles of the speed change device of FIG. 7 are identicalwith those of the second embodiment as shown in FIG. 6, and hence, theconditions of Table II are also applicable to the modification of FIG.7. The advantage of this embodiment is in the fact that the torqueconverter V can be connected to the right hand end of the crankshaft 1,as viewed in FIG. 7, so that the driving torque can be delivered to theplanetary gear assembly from the right hand end of the input shaft 11,even though the example of FIG. 7 has a torque converter connected tothe extreme left end of the crankshaft 1.

FIG. 8 shows another modification of the speed change device as shown inFIG. 7, in which modifications are made in that the positions of thefirst clutch 12, 14 and the second clutch 12, 13 are interchanged, thatthe position of the combination of the first planet gears 17 and thefirst internal gear 41 is interchanged with that of another combinationof the second planet gears 20 and the second internal gear 42, that thebrake element including a one-way brake 23, a brake 24, and a brake arepositioned between the second clutch 12, 13 and the planetary gearassembly, and that the output pinion 27 is disposed between theplanetary gear assembly and the forward clutch 12', 14. The operativeprinciples of this embodiment are identical with the second embodimentas shown in FIG. 6, and hence, the conditions of Table II are alsoapplicable to this modification. The advantage of this modification isin the fact that the power can be delivered to the planetary gearassembly from the right hand end of the crankshaft, if so desired.

It should be noted that in this embodiment, a shaft 16', whichcorresponds to the solid shaft 16 of the second embodiment of FIG. 6,should be hollow.

FIG. 9 shows a third moduification of the second embodiment as shown inFIG. 6, in which a brake 24 for stopping rotation of a sun gear 43 isplaced at the right hand end of the speed change device, as viewed inFIG. 9, so that frictional elements comprising the brake 2-4, a brake25, and a one-way brake 23 are all concentrated at the right hand sideof the speed change device.

As shown in the aforesaid second embodiment and the modifications, theoutput of the speed change device is ultimately transmitted to driveaxles 33, 34, which are disposed in parallel with a common axis ofrotation of the planetary gear assembly, clutches, and brakes. Moreover,bothsaid common axis of rotation and the drive axles are arranged inparallel with the axis of the crankshaft 1. Such arrangement of thespeed change device is advantageous for a vehicle having an enginedisposed at right angles to the tranvelling direction of the vehicle.More particularly, the arrangement is useful for the aforesaid laterallayout. of the engine in a front-engine frontdrive type vehicle or arear-engine rear-drive type vehicle.

As illustrated in FIGS. 6 to 9, in the'second embodiment of theinvention, a pair of clutches 12, 13 and 12, 14 are inserted between theinput shaft 11 and the sun gear 43 and between the input shaft 11 andthe first internal gear 41, respectively, while the output pinion 27 isdisposed either between the pair of clutches and the planetary gearassembly or between one of the pair of the clutches are the planetarygear assembly. The output pinion 27 is placed at a positioncorresponding to the longitudinal middle point of the crankshaft 1. Withthe output pinion thus disposed at an intermediate position amongmechanical elements of the speed change device according to the presentinvention, a differential gear means comprising gears 28, 29, 30, 31,and 32 can be placed at about the middle of the wheels (not shown) onboth sides of the vehicle. Accordingly, both side axles 33, and 34 canbe made in about the same length. With the aforesaid variety ofmodifications, a most suitable layout can be worked out for variouscombinations of vehicle bodies, engines, and other vehicle parts of widerange of dimensions.

FIG. 11 shows a third embodiment of the present invention, in which twounits of simple planetary gear assemblies are used. The input portion ofthe power transmission route from a crankshaft 1 to first and a secondclutch of the third embodiment is identical with the correspondingportion of the first and second embodiment of the present invention, andhence, detailed explanation of the input portion of this embodimentwillnot be re peated hereinafter.

The first clutch 1 2, 14 is connected to the internal gear 52 of'a firstsimple planetary gear assembly througha shaft 16, and the second clutch12, 13 is connected to sun gears 50 and 54 of the first and a secondsimple planetary gear assemblies through a hollow shaft 15, which hollowshaft 15 is adapted to revolve around the shaft 16. v

The first simple planet gear assembly comprises a sun gear 50 secured tothe hollow shaft 15, planet gears 51, an internal gear 52 secured to theshaft 16, and a carrier 53 supporting said planet gears 51 in arotatable manner. The planet gears 51 are meshed with both the sun gear50 and the internal gear 52, and they are adapted to turn around theaxis of the first planet gear assembly in a coaxial manner. The secondsimple planet gear assembly comprises a sun gear 54 secured to thehollow shaft 15, an internal gear 56 bonded to the carrier 53 of thefirst simple planetary. gear assembly through a hollow shaft 26, planetgears 55 meshed with both the sun gear 54 and the internal gear 56, anda carrier 57 supporting said planet gears 55 in a rotatable manner. Theplanet gears 55 of the second simple planetary gear assembly are adaptedto turn around the axis of the second simple planet gear assembly in acoaxial manner.

As shown in FIG. 11, the sun gears 50 and 54 of the first and secondsimple planet gear assemblies are bonded together by a hollow shaft 15connected to the second clutch 12, 13 so that both sun gears rotate asan integral body when the second clutch is engaged. An output pinion 27is secured to the other hollow shaft 26 connected to both the internalgear 56 of the second simple planetary gear assembly and the carrier 53of the first planetary gear assembly, so that the output pinion 27revolves integrally with the hollow shaft 26.

A one-way brake 58 mounted on a casing 35 of the speed change device isadapted to allow rotation of the carrier 57 of the second simpleplanetary gear assembly in the normal direction only, but to hold thecarrier 57 stationary when the carrier 57 tends to revolve in theopposite direction. A brake 59 acts to stop the sun gears 50 and 54 bystopping the hollow shaft 15 on which the sun gears are secured, whileanother brake 60 acts to stop the carrier 57, when such brakes areactuated. These brakes can be of band brake type, cone clutch type,multiplate clutch type, or the like, and they should be capable ofholding the aforesaid rotary members stationary with respect to thecasing 35 of the speed change device.

The output pinion 27 is meshed with a reducing gear wheel 28, whichactuates a differential gear means including gears 29, 30, 31, and 32.The manner in which the power on the turbine 3 is delivered to the bothside axles 33 and 34 is identical with the corresponding powertransmission in the first and second embodiments as described in detailhereinbefore referring to'FIGS. 1 and 6, respectively. Hence, thedetails of such output portion of the power transmission mechanism inthe third embodiment will not be repeated here.

Prior to entering into the detailed description of the operativeconditions of each brake and each clutch, power transmission routes, andthe speed change ratios for each operative stage of the speed changedevice, the symbols to be used in the following description and therelations between revolving speeds of various rotary members will now beexplained. If it is assumed that the revolving speed of the internalgear 52, the sun gear 50, and the carrier 53 of the first simpleplanetary gear assembly are represented by R S 1, and C respectively,and the corresponding revolving speeds of the internal gear 56, the sungear 54, and the carrier 57 of the second simple planetary gear assemblyare represented by R S and C respectively, then there are followingrelations between such revolving speeds.

(pitch circle radius of the sun gear 54) As will be described in detailhereinafter, in the case of forward stage operation, the first clutch12, 14 is engaged, so that the power on the turbine 3 is transmitted tothe internal gear 52 of the first planetary gear assembly through thetransmission shaft 16, while in the case of rearward operation, thesecond clutch 12, 13 is engaged, and the power on the turbine 3 istransmitted to sun gears 50 and 54 through the hollow shaft 15-. Theoutput power is delivered, in either operation, to the bondedcombination of the carrier 53 and the internal gear 56. Thus, the speedchange ratio can be defined by R /C (or R /R in the case of the forwardoperation, while the speed change ratio for the rearward operation canbe given by S /R (or S /C The expression in the parenthesis is due tothe relation of C =R If it is further assumed that the pitch circleradfi of the transmission gears 8 and 10 are identical, then the valuesof S and R will become the same as the revolving speed of the turbine 3.Furthermore, due to the fact that the revolving speed of the outputpinion 27 is the very revolving speed of the carrier 53 and the internalgear 56, each of the aforesaid speed change ratios R /C and S /C becomesthe speed change ratio between the turbine 3 and the output pinion 27.By substituting zero to the revolving speed of that rotary member whichis held stationary during each operative stage in the aforesaid Formulaea, ,3, 'y, and 5, the speed change ratios for each of such stages ofoperation can be determined.

The operative conditions in each operative stage of the speed changedevice as illustrated in FIG. 11 will now be described. As the numeralexample of the speed change ratio calculation in the succeedingdescription, it has been assumed that l -=l =2.4.

NEUTRAL STAGE Both the first and the second clutches are disengaged,while the brakes are either actuated or not actuated. Under theseconditions, the clutch body 12 idles, and the power on the turbine 3cannot be transmitted any further than the clutch body 12.

FORWARD FIRST STAGE The first clutch 12, 14 is engaged. Under theseconditions, the power on the turbine 3 is transmitted to the internalgear 52 of the first planetary gear assembly. The carrier 57 of thesecond simple planetary gear assembly tends to be rotated in thenon-normal direction due to the friction between the driving wheel ofthe vehicle and the road surface, however, the one-way brake 58 acts tohold the carrier 57 stationary against such tendency. By substitutingthe relation of C =0 into the Formulae a", B", 'y, and 6, the speedchange ratio m for this stage can be determined as follows.

In other words, the output pinion 27 revolves at a speed slower than therevolving speed of the internal gear 52 of the first simple planetarygear assembly. The power on the output pinion 27 is further delivered tothe reducing gear wheel 28 at a reduced speed, and then further to drivewheels (not shown) of the vehicle through the both side drive axles 33and 34, which are connected to th differential gear assembly.

FORWARD SECOND STAGE The forward clutch 12, 14 is engaged and the brake59 is actuated. Under these conditions, the power on the turbine 3 isdelivered to the internal gear 52 of the first simple planetary gearassembly, as in the case of the forward first stage, and sun gears 50and 54 are held stationary by means of the brake 59. By substituting thecondition of S =0 to the Formula a", the speed change ratio In for thisoperative stage can be determined as follows.

In this case, the output pinion 27 revolves also at a speed slower thanthat of the internal gear 52 of the first simple planetary gearassembly. The power transmission route from the output pinion 27 to thedrive wheels is identical with that of the forward first stage, andhence no detail explanation thereof in this and the succeeding operativestages will be repeated here.

FORWARD THIRD STAGE Both the first clutch 12, 14 and the second clutch12, 13 are engaged simultaneously, while no brake is actuated. In thiscase, the power on the turbine 3 is delivered to the sun gears 50 and 54simultaneously. By substituting the relation of S =R to the Formula cc",the speed change ratio mfor this operative stage can be determined asfollows.

In other words, the entire planetary gear assembly and the output pinion27 are rotated as an integral body at the same revolving speed.

REARWARD STAGE In other words, the output pinion 27 is rotated at areduced speed in the rearward direction.

The operative conditions of each clutch and brake in each operativestage of the speed change device as illus trated in FIG. 11 can besummarized as shown in Table III.

blies is such that a transmission shaft connected to a second clutchplate 13 is extended through the axis of the planetary gear assemblies,and, hence the shaft 15 can be made as a solid shaft. In the precedingexamples, the shaft. 15 is a hollow shaft having a large diameter. Theoperative principles of this modification are the same as those of thethird embodiment as shown in FIG. 11, and hence, the conditions of TableIII are also applicable to the device of FIG. 13. The advantage of thismodification is in the fact that the diameter of a hollow shaft 26connecting a carrier 53 with an internal gear 56 can be reduced becauseit is mounted directly on a solid shaft 15, while it was mounted onanother hollow shaft in the preceding examples. Accordingly, it is alsopossible to use a smaller pitch circle for the output pinion 27 thanthat in the preceding examples as shown in FIGS. 11 and 12. Thismodification has another advantage in the structural arrangement of thespeed change device, namely the clutches 12,13 and 12, 14 can be groupedtogetherat the left hand side of the simple planetary gear assemblies,While the other frictional elements including the one-way brake 58 andbrakes 59 and can be collected at the right hand side thereof.

TABLE III Forward Forward Forward Rearward Operative stage 1st stage 2dstage 3d stage stage First clutch (12, 14) Engaged Engaged EngagedDisengaged. Second clutch (12, 13) Disengaged Dlsengaged. do Engaged.Brake (59) Not aetuatedm. Aetuated Not actuated Not actuated. Brake (60)(Actuated) Not actuated ..do Actuated. One-way brake (58). Actuated .-dodo Not actuated. Speed Change ratio ('01.

Formula 31+ 32+1fla1 lai+lllai 1 la2.

Example: Z31=l32=2.4 2.42 1.42 1 .4.

Note: In Table III, the reason for parenthesizing the actuated conditionof the brake 60 in the forward first stage is as follows.

In the normal running of the vehicle with the speed change deviceoperated at the forward first stage, carrier 57 is apt to be rotated inthe non-normal direction by the friction between the tire and the roadsurface, but such tendency is effectively suppressed by the one-waybrake 58. When engine brake is applied, for instance for the purpose ofcontrolling the travelling speed of a vehicle while descending along aslope, there is produced such a torque on the output pinion 27 whichtends to accelerate rotation of the carrier 57 in the normal direction.Since the one-way brake 58 is not effective in hindering the rotation ofthe carrier in the normal direction, in order to make the engine brakeeffective, it is preferable to actuate the brake 60 to withhold thecarrier 57 securely.

Thus, the desired engine brake can be applied while maintaining thefirst speed change ratio.

FIG. 12 shows a modification of the third embodiment as shown in FIG.11, in which the second clutch 12, 13 is separated from the first clutch12, 14 and located at the opposite side of the planetary gearassemblies. The operative principles of the speed change device of FIG.12 are identical with those as described in detail referring to FIG. 11,and hence, the conditions of Table III are also applicable to thismodification. The advantage of this modification is in the fact that thetorque converter V can be connected to the right hand end of thecrankshaft 1, as viewed in FIG. 12, so that the driving torque can bedelivered to the planetary gear assemblies from the right hand end ofthe input shaft 11, even though the example of FIG. 12 has a torqueconverter connected to the extreme left end of the crankshaft 1.

FIG. 13 illustrates another modification of the third embodiment asshown in FIG. 11, in which the interrelation between the two simpleplanetary gear assem- FIG. 14 shows a fourth embodiment of the presentin-.

vention, which is similar to the preceding example as shown in FIG. 13except that an additional one-way brake 61 and an extra brake 62 areprovided on the transmission shaft 15. The purpose of the additionalone-way brake 61 and the brake 62 is to ensure smooth shift from theforward second stage to the forward third stage of operation.

To illustrate the use of the one-way brake 61, the function of theone-way brake 58 will be reviewed. In shifting from the forward first tothe forward second stages of the operation, sun gears 50 and 54, whichrotate in the non-normal direction in the forward first stage, are goingto be stopped by the actuation of a brake 59, and at the same time, acarrier 57, which is held stationary in the forward first stage by theone-way brake 58, is going to start rotating in the normal direction.The start of the normal rotation of the carrier 57 should be insynchronism with the stoppage of the sun gear 50 and 54, and in fact,such synchronization is achieved easily by using the one way brake 58allowing the free rotation of the carrier 57 in the normal direction. Ifthe device 58 were not a one-way brake but a two-way brake, theoperation of such imaginary brake should be properly synchronized withthat of the brake 59. In the actual operation, such proper synchronismcannot necessarily be achieved with ease, and the shift from the firstto the second operative stages tends to be uneven. Thus, with the use ofthe one-way brake 5 8, the smooth shift be tween the first and secondstages is ensured.

In the fourth embodiment of the invention, it is intended to achievesuch smooth shift in the case of the change-over from the forward secondto the forward third stages of operation. The operative conditions ofeach clutch and brake of the speed change device of FIG. 14 are shown inTable IV.

TABLE IV Forward Forward Forward Rearward Operative stage 1st stage 2dstage 3d stage stage First clutch (12, 14) Engaged Engaged EngagedDisengaged. Second clutch (12, 13) Disengaged- Disengaged. r do Engaged.Brake (59) Not actuated (Actuated). Not actuated Not actuated. Brake(60) r (Actuated) Not actuated do Actuated. Brake (62) Not actuateduqActuated o Not actuated. One-way brake (58) Actuated Not actuated do Do.One-way brake (61) Not actuated Actuated do Do.

Note: The parenthesized expression of (actuated) in Table IV representsthe fact that the related brakes are actuated under the condition ofengine brake application. The asterisk mark represents that it ispermissible to actuate the related brake.

In comparison of Table III and IV, it is apparent that with theconstruction of the fourth embodiment of the invention, to run the speedchange device of FIG. 14 at the forward second stage, the brake 62isactuated instead of the brake 59, which brake is actuated in the forwardsecond stage in the case of examples shown in FIGS. 11 to 13. The shiftfrom the forward second to the forward third stages of operation of thespeed change device can be carried out. smoothly in the followingfashion.

In the forward second stage, the sun gears 50 and 54, which tend torotate in the non-normal direction due to the friction between thedriving wheels of a vehicle and the road surface, are held stationary bymeans of the one-way brake 61, while the carrier 57 rotates at a reducedspeed. As the rearward brake 12, 13 is engaged to shift the speed changedevice into the forward third stage, the sun gears 50 and 54 startrotating in the normal direction at a gradually increasing speed, and atthe same time the revolving speed of the carrier 57 is also graduallyincreased. In this process of shifting, there is no need of adjustmentfor synchronizing the actuation of the rearward clutch 12, 13 withrelease of a related brake, because the one-way brake 61 allows, bynature, the free rotation of the sun gears 50 and 54 in the normaldirection.

FIG. shows a partial sectional view of the actual arrangement of a speedchange device according to the principles as described hereinbeforereferring to FIG. 14, showing a portion between the input shaft 11 andthe output pinion 27 coupled with the gear wheel 28. Referring to thefigure, a carrier 53 of one of the two simple planetary gear assembliesis connected to an internal gear 56 of the other simple planetary gearassembly by splining through a connecting member 64. An output pinion 27is splined to the carrier 53. Thus, the carrier 53, the internal gear56, and the output pinion 27 are rotated together as an integral body.Antifriction bearings 63 are provided on both sides of the output pinion27 to bearthe reactional force and thrust force transmitted from thereducing gear wheel 28.

In this particular arrangement, the sun gear 50 of one simple planetarygear assembly is splined to a transmission shaft 15 bonded to a secondclutch plate 13, while the sun gear 54 of the other simple planetarygear assembly is made as in integral part of the transmission shaft 15.The internal gear 52 is connected to a first clutch plate 14 through aconnecting member 14. The carrier 57 is rotatably mounted on thetransmission shaft 15 of the speed change device, and there are provideda brake 60 and a one-way brake 58 between the carrier 57 and the casing35. Toward the extreme right end of the transmission shaft 15, as seenin FIG. 15, there are provided a brake 59, a one-way brake 61, andanother brake 62 disposed between the shaft 15 and the casing 35 of thespeed change device. In the figure, the reference numeral 100 designatesa ball bearing to support an assembly of the output pinion 27, thecarrier 53 and the internal gear 56 on the casing 35 of the speed changedevice, and 101 and 102 are spring means to control actuation of theclutch means in conjunction with fluid pressure delivered through fluidpassageway 103. The reference numeral 104 represents piston rings.

As described in the foregoing referring to different embodiments andmodifications of the present invention, the output power of the speedchange device is ultimately transmitted to drive axles 33, 34, which aredisposed in parallel with the common axis of the planetary gearassemblies, clutches, and brakes. Moreover, both said common axialcenter line and the drive axles are arranged in parallel with the axisof the crankshaft 1 of the drivin'g engine. Such arrangement of thespeed change device is particularly advantageous for lateral layout ofthe engine in a front-engine front-drive type vehicle or a rearenginerear-drive type vehicle.

In the third and fourth embodiments of the invention, the output pinion27 is disposed at an intermediate position between the first and secondsimple planetary gear assemblies. With the output pinion 27 thusdisposed between two sets of planetary gear assemblies, it is made easyto place a reducing gear wheel 28 and a differential gear meanscomprising gears 29, 30, 31, and 32 at about the middle of both sidedrive wheels (not shown) of a vehicle. Accordingly, the drive axles 33and 34 to be disposed at both sides of the vehicle can be made insubstantially the same length.

With the aforesaid variety of modifications, it is always possible toselect the most suitable layout of speed change device for eachparticular structure of vehicle, which structure is determined by thedimensions of the vehicle body, engines and other accessories thereof.Thus, the optimum efiiciency of the speed change device and the mosteconomical layout of the power transmission system of a vehicle can beachieved.

What we claim is:

1. A speed change device for vehicles, comprising, in combination, atorque converter connected to one end of the crankshaft of an engine fordriving the vehicle; a first clutch and a second clutch driven by saidtorque converter; a planetary gear assembly means selectively engageablewith said first and second clutches, said planetary gear assemblyconsisting of a first sun gear connected to said first clutch, a secondsun gear connected to said second clutch, an internal gear, a pluralityof first planet gears meshed with said first sun gear, a plurality ofsecond planet gears meshed with said second sun gear, said second planetgears further meshed with both said first planet gears and said internalgear, and a carrier supporting said first and second planet gears in arotatable manner; an output gear bonded to said internal gear; and brakemeans consisting of a first brake capable of stopping said second sungear, a second brake capable of stopping said carrier, and a one-waybrake allowing said carrier to rotate in a predetermined direction butnot in the opposite direction; axes of rotation of said clutches, saidplanetary gear assembly means, said brake means, and said output gearbeing disposed in alignment with a common axis which is parallel withthe axis of said crankshaft, said output gear being located at aposition on said common axis which substantially corresponds to thelongitudinal middle point of said crankshaft.

2. A speed change device according to claim 1, wherein said first andsecond clutches are located intermediate between said torque converterand said planetary gear assembly; said first brake is mounted in theproximity of said second clutch; and said one-way brake and said 19second brake are moutned on the casing of the speed change device onthat end of the planetary gear assembly which is opposite to said torqueconverter.

3. A speed change device according to claim 1, wherein said first andsecond clutches are disposed separately on opposite sides of saidplanetary gear assembly, and said output gear is located between saidplanetary gear assembly and said second clutch, said second clutch beingpositioned between said planetary gear assembly and said torqueconverter; said first brakeis mounted in the proximity of said secondclutch; and said one-way brake and said second brake are mounted on thecasing of the speed change device on that end of the planetary gearassembly which is opposite to said torque converter.

4. A speed change device according to claim 1, wherein said first andsecond clutches are disposed separately on opposite sides of saidplanetary gear assembly, said second clutch being positioned betweensaid planetary gear assembly and said torque converter, said output gearbeing located between said planetary gear assembly and said firstclutch; and said first brake is mounted in the proximity of said secondclutch.

5. A speed change device according to claim 1, wherein said output gearmounted to said internal gear is disposed between said planetary gearassembly and said first and second clutches, said first and secondclutches being located intermediate between's'aid torque converter andsaid planetary gear assembly; and said one-way brake and said first andsecond brakes are mounted on'that side of the planetary gear assemblywhich is opposite to said torque converter.

References Cited UNITED STATES PATENTS 643,130 2/1900 Heermans 746951,125,140 1/1915 Lucke 74701 X 2,725,762 12/1955 Hettinger, et al 746882,919,604 1/1960 De Lorean 74688 X 3,025,721 3/1962 De Lorean 746883,029,662 4/1962 Hause 74668 X 3,209,617 10/1965 'Kalversberg 746883,246,542 4/1966 Moan 74688 X 3,270,585 9/1966 Livezey 74688 X 3,300,0011/1967 Stockton 74763 X 3,314,307 4/1967 Egbert 74688 ARTHUR T. MCKEON,Primary Examiner US. Cl. X.R. 74688, 701

